Timing circuit



Aug. 14, 1962 T. J. BURKE ET AL 3,049,649

TIMING CIRCUIT Filed Oct. 20. 1959 j Con/ro/ use 26V DC Gurrenf in coil 3 Current in /7 2 Closed Nef relay currem 0 Contacts 8 8 9 Confocfs 8 8 7 Closed I Thres ho/d level to operate contacts 8 8 9 Close a r Measure C/osea I l I l l I l l 77me in Mill/seconds INVENTORS Thomas .1 Bur/re Miles 6. Johnson ATTORNEYS 3,049,649 Patented Aug. 14, 1962 3,049,649 TIMING CiRCUlT Thomas J. Burke, Westmont, and Miles C. Johnson,

Mount Holly, Nl, assignors, by mesne assignments, to

the United States of America as represented by the Secretary of the Navy Filed Oct. 20, 1%9, Ser. No. 847,671 2 Claims. (Cl. 317i4l) This invention relates to a system for providing low impedance variation free current or voltage pulses and more specifically to a simple means of accurately controlling the open and closed time of relay contacts.

While not limited thereto, this invention is useful in electronic data processing equipment and more particularly to equipment requiring timing pulses of accurate predetermined lengths. In data processing systems it is generally required that the timing pulses be of accurate predetermined length and that their waveform be free from variations such as those caused by relay contact bounce. For this reason it is customary to use electronically generated timing pulses rather than pulses generated by a relay. As is well known in the art, when a relay solenoid is energized the contacts come together with such force that the normal energizing current is not capable of preventing the contacts from bouncing in a decaying oscillatory manner. Because of this, and the fact that it is very difficult to accurately control the open and closed time of the contacts of the relay, electronic timing generators have been employed to a substantial extent. It would, however, be highly advantageous under certain conditions to use a relay timing device in place of the electronic timing device, because it is small and compact in size and can be manufactured at low cost. The present invention avoids the aforementioned disadvantages of prior art by providing an improved relay timing device which is free from such defects. More specifically, there has been provided a system for accurately controlling the open or closed time of relay contacts and for preventing contact bounce.

In the present invention there is provided a polarized relay of the type employing a permanent magnet. As is well known in the art these relays have the inherent advantage of producing strong mechanical forces with relatively weak electric currents in the operating coil because a strong magnetic field is already present through the use of a permanent magnet. Hence these relays do not need magnetizing currents but require only operating currents.

In the present system the relay is provided with two windings wound in opposite directions. To one of these windings is connected a differentiating circuit, the other winding being associated with an integrating circuit. Energization of the difierentiating circuit causes the relay contacts to close. As the capacitor of the difierentiating circuit becomes charged, the current in the winding begins to decay. A closed relay contact allows current to flow to the integrating circuit thus allowing current to build up in the second winding of the polarized relay. The build up of current in the winding associated with the integrating circuit is simultaneous with the decay of current in winding associated with the differentiating circuit. By properly adjusting the variable resistor in the integrating circuit it is possible to accurately control the closed contact time.

Also inherent in this system is the fact that the total current applied to the relay is at a maximum upon closure of the contacts. This current is of such magnitude that it aids in preventing the contact bounce upon closure.

With the foregoing in mind an object of the invention is to provide an improved relay device in which the contact closure time may be accurately timed.

Another object of the instant invention is to provide a relay system having contacts free from bounce.

Still another object of the present invention resides in the provision of a timing generator which is small and compact in size and inexpensive to manufacture.

A further object is to provide a simple timing device which may be used in data processing equipment.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings showing by way of example one embodiment of the invention and wherein:

PEG. 1 is a diagram of the system of the present invention; and

FIG. 2 is a timing diagram illustrating the operation of the system of the present invention.

Referring now to the drawings, the improved timing device comprises a polarized relay 1 having windings 2 and 3 wound thereon in opposite directions. Each of these windings is connected to ground terminal 4. The opposite end of winding 2 is shunted to ground by means of capacitor 5. Connected to winding 2 is variable resister 6 which is coupled to power source 13 by means of relay armature 8 and contact point 7. Grounded resistor 15 is connected to winding 3 by means of capacitor 14, capacitor 14 being supplied by power through manual switch 16. The relay is also provided with extra contacts 11 and 12, which operate identically to contacts 7 and 9 and may be used for any external purpose.

Referring now to the operation of the system, when manual switch 16 is closed capacitor '14 charges through winding 3. The high charging current for capacitor 14 causes armature 8 to move to contact 7 thus applying current to capacitor 5 and relay winding 2 through variable resistor 6. As capacitor 14 reaches full charge the current in winding 3 has decayed to a minimum and simultaneously therewith the current in coil 2 approaches a maximum due to the fact that capacitor 5 has reached full charge. It is these simultaneous currents applied to coils 2 and 3 that cause relay armature 8 to open from contact 7. The period of time that contact 7 remains connected to source 13 depends upon the size of components 5, 6 and 14. By the foregoing it can be readily seen that contacts 7 and 12 may be closed for any predetermined period of time depending solely upon the size and adjustment of various elements of the circuit.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A system for maintaining a relay in a predetermined state for a fixed predetermined time comprising a connection for a source of power, a ground connection, a polarized relay having a set of normally open contacts and a pair of windings wound in opposite directions, each of said windings having one end connected to said ground connection, a grounded resistor, a capacitor coupling a first of said windings to said resistor, an operating switch interposed between said power connection and the junction between the capacitor and resistor, a second capacitor shunting said second winding to ground and the serial combination of a variable resistance and said normally open contacts between said second winding and said power connection.

2. A timing circuit comprising a polarized relay having at least two windings thereon, with one terminal of each winding connected to ground, a source of power, a differentiating circuit selectively connecting the ungrounded terminal of one of said windings to said power source to energize said relay to one predetermined state and an integrating circuit connected to the ungrounded terminal of the other of said windings and eifective only when said relay is in said one predetermined state to cause said relay to change to a second predetermined state.

References Cited in the file of this patent UNITED STATES PATENTS Rosing Mar. 16, 1948 Holden Aug. 15, 1950 FOREIGN PATENTS Germany Nov. 12, 1942 Germany Jan. 4, 1954 

